If you want to find a date after a cer­tain num­ber of work­days, you can use the WORKDAY func­tion. You just need the start date and the num­ber of work­ing days (Fig. 1). 

Date after X work days
 WORKDAY function
Fig. 1 WORKDAY function

We can see that Excel shows the date after the cor­re­spond­ing num­ber of work­ing days. You have to remem­ber that the WORKDAY func­tion does­n’t con­sid­er the start date in its cal­cu­la­tions. It means that if you have only one work­day, you will go to the next work­ing day (Fig. 2). 

Next working day
Fig. 2 Next work­ing day

In the WORKDAY func­tion, you can even add hol­i­days by just select­ing a range with prop­er dates. Remem­ber to lock it (F4) (Fig. 3). 

Adding holidays
Fig. 3 Adding holidays

We can see that our dates are a bit changed (Fig. 4). 

Dates changed
Fig. 4 Dates changed

The WORKDAY func­tion con­sid­ers the week­end as Sat­ur­day and Sun­day, which is cor­rect in most of the coun­tries, how­ev­er we can mod­i­fy it. When we want only Sun­day to be our week­end, we have to choose the WEEKDAYS.INTL func­tion. The func­tion con­sists of the start date and the num­ber of work­ing days. The third argu­ment is the week­end, where we can change the week­end days. Let’s choose Sun­day (Fig. 5). 

Sunday as the weekend
Fig. 5 Sun­day as the weekend

Then, we are choos­ing hol­i­days by select­ing a prop­er range and lock­ing it (F4 key). Our for­mu­la is ready (Fig. 6). 

=WORKDAY.INTL(A2,B2,11,$F$2:$F$3)

Our formula
Fig. 6 Our formula

We can see that our results dif­fer from the the pre­vi­ous ones because now Sat­ur­day is our work­ing day (Fig. 7). 

Saturday as a working day
Fig. 7 Sat­ur­day as a work­ing day